The markets have been propped up in such a fragile way that doesn't matter what pushes them over - once that Jenga tower starts to fall, gravity takes over at 9.8 m/s^2.
I agree that coronavirus itself isn't a huge deal. But it doesn't have to be anything big to expose the irrationality of the world economy. Here in the US alone, there is probably trillions in consumer debt (home/auto/student loans + revolving debt) that would go into default with a couple missed paycheck cycles. Businesses have been operating just as foolishly. The markets have been ignoring that while simultaneously making silly predictions about future growth, and those illusions just got ripped away. The fact that the markets didn't go on a big tear after last week's Fed rate cut was the indication that we're suddenly playing by different rules.
It's possible that this all blows over in a month or two, and that we'll be back to Dow 30k by summer. But man, I remember similar predictions in 2008, and the "rational optimists" got their faces ripped off by what followed.
Last time we had too big to fail.
Had we let the losers lose than opportunity would have been created in the vacuum.
Instead the losers were rewarded and the result was no correction just stagnation.
The markets were exposed as a fallacy. It neither punishes bad decision making nor rewards good decision making.
If this blip is allowed to run its course without undue interference it will pass.
Of course though politics is interfering.
As last time efforts are being made on the side of one political agenda.